Introduction:
In industrial production, a small amount of saffron T emissions will cause increase of water color
and increase of chemical oxygen consumption, so study of the decolorization of saffron T wastewater has an important
practical significance.
Methods:
MCM (Mobil Composition of Matter)-41 molecular sieve was synthesized by hydrothermal method. Power Xray diffraction and scanning electron microscopy were used to characterize the sample. Safranine T dye was adsorbed
from water by the MCM-41 prepared. Kinetics and thermodynamics of the adsorption were studied.
Results:
The MCM-41 sample presented spherical particles and regular. The BET (Brunner-Emmett-Teller) specific
surface area of the sample determined by 77 K low temperature nitrogen adsorption-desorption isotherm was 932 m2
/g. Its
average particle diameter was 110 nm. TEM (transmission electron microscopy) results showed that the sample structure
presented a honeycomb pore structure and the average pore diameter was 3.0 nm. The results showed that when room
temperature was 20 ± 1 ℃, adsorbate safranine T: adsorbent MCM-41 = 20 : 1，the optimum pH value of adsorption was
4.0 and contact time was 20 min, the adsorption rate reached 98.29% and the adsorption capacity was 19.66 mg/g. The
entropy change and enthalpy change of the adsorption system are respectively ΔS0 = 157.5 J/(mol·K); ΔH0 = 21.544
kJ/mol. When temperature was 277.15, 293.15, 303.15 K，the free energy change was respectively △G1 0 = -22.107
kJ/mol, △G2
0 = -24.627 kJ/mol, △G3
0 = -26.202 kJ/mol.
Conclusion:
The adsorption of safranine T by MCM-41 belongs to a pseudo-second-order adsorption. This adsorption
accords with the Freundlich equation and belongs to a heterogeneous adsorption. The adsorption is an endothermic
reaction of entropy increase, being spontaneous.
Comment on “Kinetics and thermodynamics of Eu(III) adsorption onto synthetic monoclinic pyrrhotite” by Y. Zhu et al., Journal of Molecular Liquids, 218 (2016), 565–570
